This is a U.S. National Stage Application of International Application No. PCT/AT99/00006 filed Jan. 11, 1999 and claims priority under 35 U.S.C. xc2xa7 119 of Austrian Patent Application No. A59/98, filed on Jan. 16, 1998.
1. Field of the Invention
The invention relates to an electric drive for a motor vehicle, in particular for a multi-track electromobile.
2. Discussion of Background Information
Such types of electric drives are being used more and more in twin-track motor vehicles, in both road and commercial vehicles. The usual design uses mainly two independent electric motors, which are geared down by a spur gear or planet gear so that the motors can run at a much higher speed than the drive gears. In this way the structural volume and the weight of the driving unit can be reduced. A considerable disadvantage however is the great expense of the individual parts.
Thus DE 26 06 807 B describes an electric motor with two side output, in the stators of which two mechanically and electrically independent rotors are excited jointly by the stator, whereby the rotors are positioned so that no end shield is necessary for the rotor bearing opposite the respective output side.
In DE 42 36 093 A a drive system for an electric vehicle is described, which comprises several motors and reducing gears with planet gear devices, which are connected in a force transmitting way between the motors and the gears of the electric vehicle, whereby the improvement is that the motors and gears are arranged coaxially, so that they can be arranged coaxially between the right and left wheel of the electric vehicle. Here all of the described driving components are arranged in a housing. By means of a suitable choice of force transmission by means of the gear devices the torque distribution to the wheel axes can be influenced advantageously.
Likewise DE 44 21 425 C describes the drive of a road vehicle with an electrical drive unit in which two separately functioning units each with an electric motor and a gear arranged facing the respective drive gear, designed as a spur gear with an output shaft arranged eccentric to the axis of rotation of the electric motor or as a planet gear, act on the drive wheels of a vehicle axis. Electric motors, gears and output shaft bearing are thus mounted on a common support member.
The disadvantage of the above described conventional drive units is the use of two mechanically and electrically independent electric motors, whereby for each drive wheel more or less the same expense is required, as a gear is also assigned to each drive wheel.
An aspect of the invention is to create an electric drive for a motor vehicle, which on the one hand avoids the disadvantages of the aforementioned drives and on the other hand is easy to assemble and meets the requirement of independent rotational speeds for the left and right drive gear of an axis.
The electric drive according to the invention is characterised in that a fixed housing is provided for the vehicle construction or for the vehicle frame, whereby in this housing a motor frame with a stator and a rotor provided in the motor frame are rotatably mounted respectively, and the motor frame and the rotor for work output rotate in opposite directions, whereby one drive line is connected with the rotor or with the motor frame and the rotational movement of the rotor or the motor frame is connected by a transmission device with the drive and output rotating in the same direction and a second drive line is connected with the motor frame or with the rotor, and the rotational movement of the motor frame is connected with the rotor and the rotational movement of the motor frame or the rotor is transmitted by a transmission device with a drive and output rotating in opposite directions. With the invention it is possible for the first time to create a drive, which is arranged between the left and the right drive wheel, which fulfills the differential function and takes up so little space that a rigid coaxial connection between the gear axes and the drive is possible without reducing the ground clearance of the vehicle to an impermissible extent. The invention is based on the fact that in every drive engine, which provides its mechanical power by means of a rotational movement, the torque on the output shaft is equal to the torque at which the engine has to be supported relative to its environment. In the conventional design with a fixed engine thus the driving power is provided exclusively by the moving output shaft. The invention however aims to achieve a branching out of output to two drive lines in order to accommodate the conditions of the vehicle drive. This can be managed according to the invention in that on the one hand the output shaft performs a rotational movement, for example the rotor, via the first drive line, on the other hand the motor frame also performs a rotational movement in an opposite direction to the rotational direction of the output shaft via the second drive line. A work output of both drive lines is achieved if the rotational movement is in the same direction as the occurring torque which is necessarily the case in the arrangement according to the invention. By Electro magnetic generation of torque, which on the one hand is picked up as an action torque on the output shaft and on the other hand exists as a reaction torque on the motor frame, there is no mechanical connection between these two parts of the arrangement, which prevents the free rotatability of both parts. In a drive for a road vehicle it is thus necessary, that the work output of the drive gears is performed with the same directional rotational movement of the right and left gear. This achieved by the drive according to the invention.
According to an embodiment variant, the motor frame is mounted by roller bearings in the housing that are in particular aligned with a shaft of the rotor. Thus, the motor frame is mounted in the housing. It is an advantage that a simple construction is possible, which ensures economical production. The motor frame can be mounted on both sides in the housing in such a way that the shaft end of the motor frame extends into the transmission device of the second drive line. By the possible short support length between the bearings, high motor speeds are possible without mechanical resonances occurring.
A further embodiment variant is provided in that the motor frame on the one hand is mounted on the shaft of the rotor and on the other hand in the housing. Thereby, a compact construction is possible.
According to another aspect of the invention, the motor-frame is mounted rotatably in the housing aligned with the shaft of the rotor having a shaft end for the bearing. Thereby, it is also ensured that both the output shaft via the rotor, and the motor frame can perform any rotational movement. As in the drive according to the invention the output is branched preferably to both sides of the electric motor corresponding bearings are provided. It is also advantageous that on the bearing no high centrifugal forces occur and relatively small bearing diameters are used.
According to another embodiment the rotor is mounted on the one hand in the housing of the drive and on the other hand in the rotating motor frame, in such a way that the shaft end of the rotor extends into the transmission device of the first drive line. In this way advantageous short paths for the torque transmission are provided.
According to a special design the drive line drives gear shafts via the transmission device. In this way it is possible advantageously to equip motor vehicles with the drive according to the invention. Thus it is possible to produce smaller and medium sized vehicles, in particular communal vehicles, economically.
The additional special design according to the present invention, the transmission devices are planet gears, whereby the rotor is securely connected via the shaft or the motor frame with a planet cage of the assigned planet gear, and moves a planet axis of at least one planet gear set. Therefore, the invention has the almost indispensable advantage for a motor vehicle that the differential function is fulfilled in the simplest manner.
For the drive device according to the invention apart from the described transmission device also spur gear, bevel gear and worm gear transmission devices are suitable which on the one hand ensure the necessary speed translation to slow between the drive shaft and gear shafts and on the other hand can obtain a reversal in rotational direction inside the transmission device.
The design according to another aspect of the present invention, the rotational movement of the rotor via the shaft or the rotational movement of the motor frame moves the planet axis at least of a planet gear set, which includes at least two rotation-fast connected gears, the axes of rotation of which rotate rigidly coupled about the axis of rotation of the shaft or the motor frame, and in that one gear of the planet gear set meshes with a sun gear arranged rotation-fast with the housing concentric to the shaft or motor frame axis, and an additional gear of the planet gear set meshes with a sun gear arranged concentrically to the shaft or motor housing, which sun gear drives the assigned gear shaft, whereby the sun gear assigned to the housing has a different diameter to the sun gear assigned to the gear shaft. This is advantageous as in one transmission step the necessary transmission between the drive and gear shags can be achieved.
According to an advantageous development, in one drive line, the sun gear assigned to the housing has a smaller diameter the sun gear assigned to the gear shaft and in the other drive line the sun gear assigned to the housing has a greater diameter than the sun gear assigned to the gear shaft. With a fixed rotational diameter of the planet sets, the transmission ratio is formed exclusively from the diameter of the larger sun gear and the difference of the diameter of the two sun gears. The desired direction of rotation of the gear shafts is obtained however with a given transmission ratio by the arrangement of the larger sun gear either fixed to the motor vehicle or connected with the gear shafts. The arrangement of the planet gears is determined necessarily by the required engagement ratios.
The design according to another aspect of the present invention, the transmission devices have the same transmission ratio. It is advantageous, as with the vehicle drive in most cases it is preferable, if at the same speed of the drive gears, for example when driving in a straight line, the drive output to the same parts is passed on to the drive gears. This is achieved by the arrangement according to the invention by having the same transmission ratios of the transmission devices for both drive lines.
The design according to another aspect of the present invention, the transmission devices have a transmission ratio, which corresponds to the ration of the diameters of the fixed sun gears. It has the advantage that any possible distribution of output to the drive lines is conceivable, when the transmissions of the gears are set in a corresponding ratio relative to one another.
The development according to to another aspect of the invention, the transmission device is designed in two stages, whereby a planet axis rotates with the shaft or with the motor frame, on which a planet gear set with three relatively fixed gears is rotatably mounted, and the planet gear set on the one hand is in arrangement with freely rotatable sun gears, which are alternatively securable by a braking device and on the other hand with the sun gear assigned to the gear shaft. It is advantageous, in that an additional sun gear that can be coupled optionally rotation fast relative to the vehicle a second transmission stage can be connected.
According to a further design, the planet cage is provided on the output side with a surface in particular with a conical frictional surface, against which a brake disc mounted rotation-fast relative to the housing is activated by an electromagnetic activating device. With this advantageous design a considerable simplification of the entire axial construction can be achieved, if for each drive line a magnetically operated braking device is provided, in which a ring fixed relative to the motor vehicle, the frictional surface of which can be designed to be conical to increase the braking torque, acts on a corresponding opposite surface on the planet cage. As the planet cage runs at the high speed of the motor, the applied braking torque is increased by the transmission of the gear, so that a much greater braking torque acts on the gear shafts. The brake can be designed in such a way that that the friction ring in a currentless state of the activating magnet is forced by sprig force against the planet cage, whereby the function of a hand brake is achieved By metering the application of the magnetic force of the activating magnet the described braking device can also be used as a pedal brake.
It is also possible however to provide a friction surface, which at the same time acts on the motor frame on the one hand and on a part of the transmission device of the rotor drive line coupled with the rotor rotation on the other. By such a braking device both drive lines can be decelerated simultaneously.
According to a design of another aspect, a mechanical brake is provided, which brakes the rotational movement of the motor frame/,and the rotational movement of the rotor, in particular simultaneously. There is a structural advantage in that in a normal case, that is with equal deceleration of both drive lines, no free reaction torque occurs which would have to be supported on the housing.
Another aspect of the invention provides a mechanical brake that acts on the outer periphery of the motor frame or on the outer periphery of the planet cage connected with the shaft. This aspect is also advantageous, as by the action of the brake on the fast rotating components the torque is increased on the gear shafts by the transmission ratio.
According to still a further aspect of the invention, the mechanical brake is in particular, a divided or slotted ring. This design has proved advantageous as a simple component is used as a brake.
A design according to another aspect of the present invention, the mechanical brake can be activated by a cable pull. With this design, it is also possible as also in this case only the simplest mechanical components can be used,
Additionally, other aspects of the present invention include a mechanical brake that can be activated magnetically, in particular, by a lifting magnet on the cable pull. This design is advantageous, because a with low activating forces a magnetic activation is entirely possible.
According to a special design for electromechanical transduction an asynchronous machine with a squirrel cage rotor is provided the rotational filed of which is generated by frequency control and the current is supplied by slip rings on the periphery of the motor frame. As with the drive according to the invention the motor frame is mounted rotatably on the associated output shaft, the supply of current to the motor must be made via slip rings on the periphery of the motor frame. For the electromechanical transduction preferably the principle of the asynchronous machine with squirrel cage rotor is suitable, the rotational field of which is generated with driving speed dependent frequency control by electronic commutation. However any kind of electric driving machine is conceivable in which a torque is produced between the stator and rotor.
In another aspect of the present invention, the housing with the motor frame and the rotor and the transmission devices and the gear shafts with their bearing form a standard component. There are economical advantages to the formation of a standard component, which extend from the manufacture, stock keeping of spare parts to sales. Furthermore, the bearing of the output side sun gears of the transmission devices can be such that it permits the accommodation of gear forces, so that no additional axial bearing is necessary. However it is also possible to attach articulated shafts, in order to reduce the unsprung mass of the motor vehicle, and if necessary to increase the ground clearance between the drive gears.
According to an aspect of the present invention, an electric drive for a motor vehicle having a vehicle structure or vehicle frame is provided including a housing adapted to be fixed relative to the vehicle structure or vehicle frame, a motor frame rotatably mounted within the housing, and a stator and rotor being mounted for relative rotation and being located within the housing, the motor frame and the rotor arranged to rotate in opposite directions for work output. The invention further includes a first driveline being connected to one of the rotor or the motor frame, wherein rotational movement of the one of the rotor or the motor frame is transmitted through a first transmission device coupled to the first driveline such that a first output of the first transmission device rotates in a same direction as the rotational movement of the one of the rotor and the motor frame; and a second driveline connected to the other of the rotor or the motor frame, wherein rotational movement of the other of the rotor or motor frame is transmitted through a second transmission device coupled to the second driveline such that a second output of the second transmission device rotates in a direction opposite the rotational movement at the other of the rotor and the motor frame, wherein each of the first and second transmission devices comprises planet gears including a planet cage and at least one planet gear set, whereby one of the rotor or the frame is connected via a shaft of the rotor or the motor frame, respectively, with the planet cage and move a planet axis of the at least one planet gear set.
According to another aspect of the present invention, the electric drive is used in a multi-track electromobile. In another aspect of the present invention, the motor frame is mounted by roller bearings in the housing. According to a further aspect of the present invention, the roller bearings are aligned with the shaft of the rotor. In another aspect of the present invention, the motor frame is mounted one of on the shaft of the rotor or on the housing.
According to a still further aspect of the present invention, the motor frame, which is rotatably mounted in the housing has a shaft end adapted for a bearing that is aligned with the shaft of the rotor. According to another aspect of the invention, the rotor is mounted one of in the housing or in the motor frame. Further aspects of the invention include wherein the first driveline drives a first gear shaft connected to the first transmission device and the second driveline drives a second gear shaft connected to the second transmission device.
According to other aspects of the present invention the housing, the motor frame, the rotor, the first and second transmissions devices, the first and second gear shafts and associated bearings for the first and second gear shafts form a standard component package.
According to an aspect of the present invention, the at least one planet gear set comprises at least two sun gears and at least a first and second gear having axes of rotation of which rotate rigidly about an axis of rotation of the shaft of the rotor or of the motor frame, wherein the first gear is arranged to mesh with one of the sun gears, which is arranged to be non-rotational with respect to the housing and concentric to the shaft of the rotor or to a motor frame axis, and the second gear is arranged to mesh with the other sun gear, which is arranged concentrically to the shaft of the rotor or the motor housing axis, the other sun gear being arranged to drive a respective gear shaft, wherein the one sun gear has a different diameter than that of the other sun gear.
According to another aspect of the present invention, the first driveline which is coupled to a first gearshaft, the one sun gear having a smaller diameter than other sun gear, which is coupled to the first gear shaft; and with the second drive line which is coupled to a second gear shaft, the one sun gear has a greater diameter than the other sun gear, which is coupled to the second gearshaft.
In another aspect of the present invention, the first and second transmission devices have a transmission ratio which corresponds to a ratio of diameters of the at least two sun gears. According to a further aspect of the present invention, the first and second transmission devices have a same transmission ratio. In another aspect of the present invention the first and second transmission devices have two stages, such that the planet axis rotates with the shaft of the rotor or with the motor frame, and the at least one planet gear set comprises three rotatably mounted gears which are positionally fixed relative to each other, the at least one planet gear set being in engagement with freely rotatable sun gears, which are alternatively securable by a braking device, and being in engagement with a another sun gear assigned to a gear shaft.
According to a still further aspect of the present invention, the planet cage is provided on an output side and includes a surface positionable against a brake disc, which is mounted to be non-rotatable relative to the housing acts, is activated by an electromagnetic activating device. In another aspect of the present invention, the surface is a conical frictional surface. According to an aspect of the present invention, a mechanical brake is arranged to brake rotational movement of the motor frame and rotational movement of the rotor.
According to another aspect of the present invention, the mechanical brake acts on an outer periphery of the motor frame or on an outer periphery oft he planet cage connected with a shaft of the rotor. In another aspect of the present invention, the mechanical brake operates simultaneously with respect to the rotational movement of the motor frame and the rotational movement of the rotor. According to a further aspect of the present invention, the mechanical brake is a divided or slotted ring.
In another aspect of the present invention, the mechanical brake can be activated by a cable pull. According to still a further aspect of the present invention, the mechanical brake can be activated magnetically. Further aspects of the invention include wherein the mechanical brake can be activated magnetically by a lifting magnet on a cable pull.
According to other aspects of the present invention, wherein for electromechanical transduction, an asynchronous machine with a squirrel-cage rotor is provided, wherein a rotational field of which is generated by frequency control and current is supplied by slip rings on a periphery of said motor frame.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.